Monosubstituted ureas as fuel additives

ABSTRACT

VARNISH-REMOVING ADDITIVES FOR LIQUID HYDROCARBON FUELS COMPRISING MONOSUBSTITUTED UREAS HAVING THE FORMULA   R-CH(-R1)-NH-CO-NH2   WHERE R IS HYDROGEN, ALKYL RO ALKENYL AND R1 IS ALKYL OR ALKENYL, AND THE SUM OF THE CARBON ATOMS IN R AND R1 IS FROM ABOUT 5 TO ABOUT 25.

United States Patent 3,677 72 MONOSUBSTITUT ADD US. C]. 44-71 8 Claims ABSTRACT OF THE DISCLOSURE Varnish-removing additives for liquid hydrocarbon fuels comprising monosubstituted ureas having the formula where R is hydrogen, alkyl or alkenyl and R is alkyl or alkenyl, and the sum of the carbon atoms in R and R is from about 5 to about 25.

This invention relates to additives for liquid hydrocarbon fuels. More specifically, it relates to hydrocarbon fuel compositions having improved varnish-removing and lacquer-removing characteristics.

Liquid hydrocarbon fuels have a tendency to form polymeric materials known as gum. Gum, which is often formed during storage of the fuel, leads to resin-like deposits in various parts of fuel systems. For example, in the case of internal combustion engines, resin-like deposits tend to form in the fuel supply lines, fuel filter, carburetor, fuel control, injectors, intake manifold and valve stems. Such deposits are objectionable not only because of their effect on mechanical performance, but also because they decrease the breathing efficiency in engines of the spark ignition type.

Hydrocarbon fuels for internal combustion engines may be broadly classified in four categories according to the use for which they are intended; fuels for automotive spark ignition engines, fuels for aircraft spark ignition engines, fuels for gas turbine engines and fuels for compression ignition engines. Although each such fuel is composed essentially of hydrocarbons, the stability characteristics during the manufacturing process and subsequent storage and use, particularly in the presence of oxygen, differ considerably for each type. For example, typical automotive fuels contain straight and branched chain aliphatics, olefins, naphthenes and some aromatics, while typical aircraft fuels contain a smaller proportion of olefins. In recent years, fuels for compression ignition engines have contained an increased proportion of cracked stocks, resulting in a higher olefin content and a consequent increase in the susceptibility to the formation of gum.

The additives of the present invention also find utility in distillate fuel oils. Thus, the phrase liquid hydrocarbon fuel, as used herein, is intended to embrace distillate fuel oils as well as fuels for internal combustion engines. It is well known that fuel oils are prone to form gum during periods of prolonged storage. This results in formation of resin-like deposits on equipment parts such as noz zles, screens, fuel lines, filters and the like, thereby causing eventual blockage or sticking and malfunctioning of the equipment.

The prior art discloses various fuel additives designed to retard the formation of gum. In contrast therewith, the present invention discloses a particular class of fuel additives which is effective in removing lacquer and varnish deposits attributable to gum after they have formed, thus behaving as a varnish stripper.

3,677,726 Patented July 18, 1972 It is an object of the present invention, therefore, to provide improved hydrocarbon fuel compositions having varnish-removing and lacquer-removing characteristics. Another object of the present invention is to provide additives for fuels which act as varnish strippers. Other aspects, objects and advantages of the present invention will be apparent from a consideration of the accompanying disclosure and the appended claims.

In the present invention it was discovered that certain monosubstituted ureas, when employed in small amounts in a hydrocarbon fuel, are effective in removing varnish and other deposits from parts exposed to the fuel, for example, the fuel-air induction system of internal combustion engines. It Was found in the present invention that, within the class of substituted ureas, only monosubstituted ureas are outstanding in removing deposits from engine induction systems when employed in the fuel. Disubstituted urea compounds, for example, do not provide the outstanding results achieved by the use of monsubstituted ureas.

'It was further discovered in the present invention that, even among the monosubstituted urea compounds, only certain of those compounds exhibit outstanding activity in removing varnish of the type found in internal combustion engines. More particularly, successful results were achieved in the present invention with monosubstituted ureas wherein the substitution group has a total carbon number of from about 5 to about 25.

The monosubstituted urea compounds which are employed as fuel additives in the present invention are represented by the following structure:

where R is hydrogen, alkyl or alkenyl and R is alkyl or alkenyl, and the sum of the carbon atoms in R and R is from about 5 to about 25 and H O R(i7NHfl-NH2 1'1 where R is alkyl or alkenyl having from 5 to 25 carbon atoms.

Preferred compounds are those monosubstituted ureas where the substituent group is primary alkyl or primary alkenyl having at least about 9 carbon atoms. Outstanding results have been achieved, with octadecylurea, dodecylurea and 9-octadecenyl urea.

The outstanding activity of the monosubstituted ureas of the present invention as varnish removers is illustrated by the results of a bench test wherein numerous urea compounds were brought into contact with a test strip coated with resinous deposits of the kind typically found in automotive engines. Because some of the urea compounds tested were not soluble in fuel at room temperature, all of the compounds were dissolved in hot oil (0.1 g. of urea compound in 20 g. SAE 10W30 base oil at C.).

A stainless steel spatula was coated in the following manner with resinous deposits from a Sequence VB test engine which had operated on a mineral lubricating oil. This type test is one of the group known as the Engine Test Sequences for Evaluating Oils for API Service MS (1963). The spatula was dipped into dimethylformamide solvent containing approximately 20% by weight of the resinous deposits, and the coating was then allowed to dry. The coated spatula was then immersed in the hot oil-urea solution for 30 minutes, removed, allowed to cool and wiped with a tissue. The portion of resin removed after wiping was visually estimated and defined as the activity percentage. Results obtained with various substituted urea compounds are set forth in Table I below wherein the substituent groups correspond to the following structure:

comprises reacting an alkyl amine with urea in approximately equivalent molecular proportions and then heating the mixture to a temperature between 100 C. and the decomposition temperature of the desired alkyl urea. Yet another process comprises the reaction of carbon monoxide, sulfur and an amine.

Typical examples of the substituents which may be TABLE I.-VARNISH REMOVAL ACTIVITY OF SUBSTITUTED UREAS (0.5% IN OIL AT 105 C.)

Activity, Compound 1 R2 Rs R4 percent 1-cyclohexy1-3-octadecylurea CuHs-- H H C13H31 Tetrabu vl rea C4Hn- C4Hn- 0 H C H o Oetadecylurea.-- O1aH37- H H H 99 t-Butylurea O(CH H H H 0 1,3-dimethylurea H: H OH;- H a g 1,3-diethylurea -C H H C H H a 0 Butylurea--. 4Ho H H H I! 0 4 0 4 t H H 0 C3H5 H H H B O -l2-C5H11 H H H 0 Methylurea -CH@ H H H a 0 1,3-diisopropylur (CHz)zCH H (CH3)2CH- H 0 1-cyclohexyl-1,3-pentylurea H H C H H 0 Dodecylurea -n-C12Hu H H 99 1-cyclohexyl-3,3-diet yl C H H -C-,H5 -CgH 0 1-eyclohexyl-3,3-diethyl-l-methylurea- C@H11 CH3 -C2H5 :His 0 l-cyclohexyl-l,3,3-triethylurea C0H11 -CzHs C2H -C H 0 l-sec-butyl-l-cyelohexyl-3,3-diethylurea C5H -sec-C H --C2Hs C2H 0 i-eyclohexyl-l,3,3-trimethy1urea --C@Hu H3 CH ---CH 0 l-cyclohexyl-1-ethyl'3,3-dimethy1urea. --CaH -Cz s CH;; ---CH;, 0 1eyelohexyl-3,3-dimethylurea -CeHn --OH.1 -CH 1-cyelohexyl-3-methylurea 'O6H11 -CH 5 l-eyclohexyl-l,3-dimethylurea 'O6H1I CH3 CH3 IE[ 5 1,1-dimethyl-3(2-ethylcyclohexyl) urea- CH3 -CH3 -(2-EtCsH H 0 1-cyclohexyl-1-ethyl-3-methylurea OHn -C2H5 CH3 H 0 1-tert-butyl-3-methyl-1-(5,5,7,7) tetramet t-C4H9 t-C5H11 -GHa C3Hm 0 l-butyl-l-cyelohexyl-B-methylurea. C5H1 C H ---CH; 11 0 l-cyelohsxyl-S-methyl-1propylure C6Hu -C3H7 --CH H 5 1-butyl-tert-butyl-3-methylurea- -C4Ho t-C4Ho OH; H 0 1-tert-butyl-1-isobutyl-3-methylure t-C H -1so-O4H -CH.-t H 0 N,N-dimethylurea-N', N -diheptylurea H3 3 -C H C H N,N-dietl1yl-N ,N'-diheptylurea C2Ht C H5 --C7H15 C1H 0 1,1,3,3-tetramethylurea --OH: CH; -GH3 CH1 0 1-(2,6 diethylcyclchexy1)3,3-dimethylurea 2 g-t)11Et- H -CH; CH; 0

G 9 1-(Z-tert-butyl-5,6-dimethylcyclohexy1-3,3-dimethyluread(i11\-f-ufi5,)6- H -CH; -C H3 10 e o s 1-(2-tert-butyl fi-etbylcyclohexyl-3,3-dimethylurea Egg-guid- H -CH; -CH; 0

0 9 1-tert-butyl-3-(2-tert-butyl-dmethylcyclohexylm'ea N([2-(t:-1% u-)6- H t-O4H9 H 5 e 6 9 1,1-diethyl-3-methylurea -CHs -C;H5 CH H 0 t-dodecylureat-CizHn H H H 50 Q-octadecenylurea C1sHas H H H 99 1,1,3-trimethylurea. CH: -CH; -CH; H 0 2-ethylhexylurea 2El3-C6Hu H H H 50 B Film became soft and mottled.

From the data in Table I it can be seen that the greatest varnish removal activity was achieved with the following primary monosubstituted ureas: octadecylurea, dodecylurea and 9-octadecenylurea. The advantage of primary substitution is illustrated by the 99% activity of dodecylurea as compared to 50% activity of tertiary dodecylurea.

To demonstrate the effectiveness of monosubstituted ureas as varnish removers for fuel systems, an engine test was conducted using 9-octadecenylurea according to the following example:

EXAMPLE 1 9-octadecenylurea was added to gasoline at concentrations from p.p.m. to 100 p.p.m., being solubilized by either isopropanol or alkylbenzene (C sulfonic acid. A single-cylinder CLR Oil Test Engine having resin-like deposits on the carburetor threat was operated on the urea-containing gasoline for approximately 24 hours. Visual inspection of the carburetor throat following the test run revealed that significant cleaning had occurred.

Monosubstituted ureas useful in the fuel compositions of the present invention may be prepared according to numerous known processes. Processes for the manufacture of monoalkylsubstituted ureas have involved the reaction of alkyl isocyanates with ammonia, the reaction of ammonium salts with alkali metal cyanates and the reaction of nitrourea with amines. Still another process present in the monosu bstituted ureas of the present invention are alkyl radicals, e.g., amyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, and other branched alkyl radicals having the formula where n is an integer up to 25; alkenyl radicals, e.g., pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, dodecenyl and other alkenyl radicals having the formula C lwhere n is an integer up to 25.

As hereinbefore mentioned, the additives of the present invention find utility in distillate fuel oils as well as in gasoline. The fuel oils that are included within the present invention are hydrocarbon fractions having an initial boiling point of at least about F. and an end boiling point no higher than about 750 F., and boiling substantially continuously throughout their distillation range. The distillate fuel oils can be straight-run distillate fuel oils, catalytically or thermally cracked (including hydrocracked) distillate fuel oils, or mixtures of straightrun distillate fuel oils, naphthas and the like, with cracked distillate stocks.

Particularly contemplated among the fuel oils are Nos. 1, 2 and 3 fuel oils used in heating and as diesel fuel oils, and the jet combustion fuels. The domestic fuel oils generally conform to the specifications set forth in ASTM Specifications D396-48T. Specifications for diesel fuels are defined in ASTM Specifications D975-48T.

Gasoline A Percent by volume Catalytically cracked gasoline 63 Straight run gasoline 17 Benzene 8 Toluene 12 (ASTM boiling range of 104 F. to 390 F. with a 50% distillation [mid-boiling] point of 203 F.)

Gasoline B Percent by volume Catalytically cracked gasoline 66 Straight run gasoline 2 Benzene 12 Toluene 8 Butanes 12 (ASTM distillation range of 80 F. to 290 F. and a midboiling point of 200 F.)

The monosubstituted ureas of the present invention may be used in motor gasoline along with other additives designed to impart other improved properties thereto. Thus, anti-knock agents, pre-ignition inhibitors, anti-rust agents, metal-deactivators, dyes, antioxidants, detergents, antistall agents, etc., may be present in the gasoline. Also, the gasoline may contain a small amount, from about 0.01 percent to about 1 percent, by weight, of a solvent oil or upperlube. Suitable oils, for example, include Coastal and Mid-Continent distillate oils having viscosities within the range of from about 50 to about 500 S.U.S. at 100 F. Synthetic oils, such as diester oils, polyalkylene glycols, silicones, phosphate esters, polypropylenes, polybutylenes and the like, may also be used.

When the monosubstituted ureas of the present invention are employed as varnish-removing additives in distillate fuel oils, the fuel oil composition can contain other additives for the purpose of achieving other results. Thus, for example, there can be present foam inhibitors and ignition and burning quality improvers. Examples of such additives are silicons, dinitropropane, amyl nitrate, metal sulfonates and the like.

Those monosubstituted ureas of the present invention which are not soluble in fuel at room temperature can be solubilized by small amounts of strong acid (0.5 mole of HCl or 1 mole of benzene sulfonic acid) or larger amounts of weak acids (approximately 2 to 3 moles of acetic acid). The action of the acid is to eliminate the crystallinity by salt formation. It has also been found that neutral calcium alkylbenzene sulfonate will solubilize 9- octadecenyl urea.

It has been found that the addition of heat to the fuel compositions of the present invention enhances the varnish-removing activity. Thus, the conduction, radiation and convection of exhaust manifold heat in internal combustion engines promote the elfectiveness of the monosubstituted urea additives in cleaning the air induction system parts. Combustion chamber radiation promotes cleaning of the intake valve area with the disclosed additives.

Considerable variation in concentration of the ureas within the fuel is alforded herein, depending upon the cleaning technique employed. For example, the urea additive may be used on an intermittent basis in some applications and on a continuous basis in others. The intermittent application would usually employ a greater concentration of urea additive, e.g., 25 p.p.m. to 300 p.p.m., particularly p.p.m. or more, in a limited batch of fuel. After the batch of urea-containing fuel is consumed and the fuel induction and air induction system is cleaned, operation on standard fuel would resume.

In some applications it may be desirable to continually operate on urea-containing fuel compositions, thus preventing recurrence of varnish deposits. For economic reasons a very low concentration would therein be employed.

It is to be understood that, for certain intermittent uses of the urea additives, more than several hundred p.p.m. of additive may be appropriate where fuel performance and economy can be sacrificed during a brief cleaning operation.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fuel composition comprising a major amount of a liquid hydrocarbon fuel and a minor amount, sufiicient to impart varnish-removing activity, of a compound having the formula where R is alkyl or alkenyl having from 5 to 25 carbon atoms.

2. A composition of claim 1 where R contains at least about 9 carbon atoms.

3. A composition of claim 1 wherein the compound is octadecylurea.

4. A composition of claim 1 wherein the compound is dodecylurea.

5. A composition of claim 1 wherein the compound is 9-octadecenylurea.

6. A composition of claim 1 wherein the fuel is a hydrocarbon mixture boiling in the gasoline boiling range.

7. A composition of claim 1 wherein the fuel is a distillate fuel oil.

8. A composition of claim 1 wherein the compound is present in a concentration from about 25 p.p.m. to about 300 p.p.m. based upon the fuel.

References Cited UNITED STATES PATENTS 2,195,167 3/1940 Egerton 44-71 X 2,002,645 5/ 1935 Rather et al 4471 X 2,991,162 7/1961 Malec 44-71 X DANIEL E. WYMAN, Primary Examiner W. J. SHINE, Assistant Examiner 

